Guidewires may have a number of sensors or sensor assemblies integrated directly into the guidewire. Such sensor-equipped guidewires may be adapted for measuring various parameters within a patient's body. Sensors typically have one or more cables passed through the guidewire for electrically coupling the sensor element to an electronic assembly that is placed outside the patient body.
Guidewires are generally comprised of a hypotube or a solid core segment and coiled segment about a core wire which may extend through the length or a partial length of the guidewire. The core wire may be fabricated from stainless steel or Nitinol with the coiled segment fabricated from a wire or braid which provide for flexibility, pushability, and kink resistance to the guidewire. Nitinol wire, used by itself or braided with stainless steel, may further help to increase flexibility and allow the wire to spring back into shape.
Moreover, guidewires have a standard diameter of 0.014 inch (about 0.3 mm) and accommodating certain types of sensors or having multiple sensors may be limited by the relatively small space provided by the guidewire. Moreover, guidewires are typically used for insertion into and advancement through the vasculature which can present an extremely tortuous pathway. Therefore, the guidewire has to be optimized for having the best mechanical performance needing a construction closer to the conventional guidewires with core wire. This further put limitation on space. In addition, if conventional conducting elements are used, the stress generated due to flexing may cause shifts in the relative position of conductors giving rise to change in electrical coupling. Additionally, having a guidewire passing through different environments (such as a blood-filled environment within the vessels and the environment external to the patient's body) may cause electrical instability within any conducting wires which pass through the length of the guidewire. Such challenges may cause undesired artifacts in measurements thus affecting sensor performance.
Guidewires incorporating one or more electrodes along their length may present additional challenges to guidewire construction and use. For instance, the presence of a plurality of electrodes along the guidewire may require additional conductive wiring passed through the length of the guidewire. Because of the limited space and flexibility required from guidewires, any sensors and/or electrodes positioned along their length are desirably correspondingly constructed.
Consequently, there is a need to design conducting elements that take up minimal space, can be long or short depending on the need, have limited changes in electrical network during operation and offer most manufacturing and process flexibility to accommodate connections to a multitude of sensing elements.